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><H1
><A
NAME="ECPG-SQL-GET-DESCRIPTOR"
></A
>GET DESCRIPTOR</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN43287"
></A
><H2
>Name</H2
>GET DESCRIPTOR&nbsp;--&nbsp;get information from an SQL descriptor area</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN43290"
></A
><H2
>Synopsis</H2
><PRE
CLASS="SYNOPSIS"
>GET DESCRIPTOR <TT
CLASS="REPLACEABLE"
><I
>descriptor_name</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>:cvariable</I
></TT
> = <TT
CLASS="REPLACEABLE"
><I
>descriptor_header_item</I
></TT
> [, ... ]
GET DESCRIPTOR <TT
CLASS="REPLACEABLE"
><I
>descriptor_name</I
></TT
> VALUE <TT
CLASS="REPLACEABLE"
><I
>column_number</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>:cvariable</I
></TT
> = <TT
CLASS="REPLACEABLE"
><I
>descriptor_item</I
></TT
> [, ... ]</PRE
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN43299"
></A
><H2
>Description</H2
><P
>     <TT
CLASS="COMMAND"
>GET DESCRIPTOR</TT
> retrieves information about a
     query result set from an SQL descriptor area and stores it into
     host variables.  A descriptor area is typically populated
     using <TT
CLASS="COMMAND"
>FETCH</TT
> or <TT
CLASS="COMMAND"
>SELECT</TT
>
     before using this command to transfer the information into host
     language variables.
    </P
><P
>     This command has two forms: The first form retrieves
     descriptor <SPAN
CLASS="QUOTE"
>"header"</SPAN
> items, which apply to the result
     set in its entirety.  One example is the row count.  The second
     form, which requires the column number as additional parameter,
     retrieves information about a particular column.  Examples are
     the column name and the actual column value.
    </P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN43307"
></A
><H2
>Parameters</H2
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><TT
CLASS="REPLACEABLE"
><I
>descriptor_name</I
></TT
></DT
><DD
><P
>        A descriptor name.
       </P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>descriptor_header_item</I
></TT
></DT
><DD
><P
>        A token identifying which header information item to retrieve.
        Only <TT
CLASS="LITERAL"
>COUNT</TT
>, to get the number of columns in the
        result set, is currently supported.
       </P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>column_number</I
></TT
></DT
><DD
><P
>        The number of the column about which information is to be
        retrieved.  The count starts at 1.
       </P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>descriptor_item</I
></TT
></DT
><DD
><P
>        A token identifying which item of information about a column
        to retrieve.  See <A
HREF="ecpg-descriptors.html#ECPG-NAMED-DESCRIPTORS"
>Section 33.7.1</A
> for
        a list of supported items.
       </P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>cvariable</I
></TT
></DT
><DD
><P
>        A host variable that will receive the data retrieved from the
        descriptor area.
       </P
></DD
></DL
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN43337"
></A
><H2
>Examples</H2
><P
>     An example to retrieve the number of columns in a result set:
</P><PRE
CLASS="PROGRAMLISTING"
>EXEC SQL GET DESCRIPTOR d :d_count = COUNT;</PRE
><P>
    </P
><P
>     An example to retrieve a data length in the first column:
</P><PRE
CLASS="PROGRAMLISTING"
>EXEC SQL GET DESCRIPTOR d VALUE 1 :d_returned_octet_length = RETURNED_OCTET_LENGTH;</PRE
><P>
    </P
><P
>     An example to retrieve the data body of the second column as a
     string:
</P><PRE
CLASS="PROGRAMLISTING"
>EXEC SQL GET DESCRIPTOR d VALUE 2 :d_data = DATA;</PRE
><P>
    </P
><P
>     Here is an example for a whole procedure of
     executing <TT
CLASS="LITERAL"
>SELECT current_database();</TT
> and showing the number of
     columns, the column data length, and the column data:
</P><PRE
CLASS="PROGRAMLISTING"
>int
main(void)
{
EXEC SQL BEGIN DECLARE SECTION;
    int  d_count;
    char d_data[1024];
    int  d_returned_octet_length;
EXEC SQL END DECLARE SECTION;

    EXEC SQL CONNECT TO testdb AS con1 USER testuser;
    EXEC SQL ALLOCATE DESCRIPTOR d;

    /* Declare, open a cursor, and assign a descriptor to the cursor  */
    EXEC SQL DECLARE cur CURSOR FOR SELECT current_database();
    EXEC SQL OPEN cur;
    EXEC SQL FETCH NEXT FROM cur INTO SQL DESCRIPTOR d;

    /* Get a number of total columns */
    EXEC SQL GET DESCRIPTOR d :d_count = COUNT;
    printf("d_count                 = %d\n", d_count);

    /* Get length of a returned column */
    EXEC SQL GET DESCRIPTOR d VALUE 1 :d_returned_octet_length = RETURNED_OCTET_LENGTH;
    printf("d_returned_octet_length = %d\n", d_returned_octet_length);

    /* Fetch the returned column as a string */
    EXEC SQL GET DESCRIPTOR d VALUE 1 :d_data = DATA;
    printf("d_data                  = %s\n", d_data);

    /* Closing */
    EXEC SQL CLOSE cur;
    EXEC SQL COMMIT;

    EXEC SQL DEALLOCATE DESCRIPTOR d;
    EXEC SQL DISCONNECT ALL;

    return 0;
}</PRE
><P>
     When the example is executed, the result will look like this:
</P><PRE
CLASS="SCREEN"
>d_count                 = 1
d_returned_octet_length = 6
d_data                  = testdb</PRE
><P>
    </P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN43349"
></A
><H2
>Compatibility</H2
><P
>     <TT
CLASS="COMMAND"
>GET DESCRIPTOR</TT
> is specified in the SQL standard.
    </P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN43353"
></A
><H2
>See Also</H2
><A
HREF="ecpg-sql-allocate-descriptor.html"
>ALLOCATE DESCRIPTOR</A
>, <A
HREF="ecpg-sql-set-descriptor.html"
>SET DESCRIPTOR</A
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